[X] My Assistant

[Decepticon]

Here's what extrapolating the current SPICE kernels yields:

IAPETUS 2005 NOV 12 14:34:49 185078153 415,451 km arcmin=12.1
IAPETUS 2006 JAN 25 21:13:08 191495653 873,345 km arcmin=5.7

IAPETUS 2006 APR 11 17:16:28 198047853 602,419 km arcmin=8.3
IAPETUS 2007 SEP 10 12:31:28 242699553 1,259 km arcmin=2186.8

Posted by jmknapp

This time a little further out.

Jan. 2006 - 879,000 km - 5.3 km/pixel - eastern Cassini Region and transition zone, part ofthe "moat" posted by VP


If anyone has made a animation of the encounter please post it!

[Decepticon]

If possible can a MOD fix my date I put 15th instead of the 25th. Thanks



Times like this I wish I was MOD.

[volcanopele]

Fixed

[Decepticon]

Sorry I sould have said in topic heading, the encounter is on

JAN 25,06

Titan is on the 15th.

[volcanopele]

Sorry I sould have said in topic heading, the encounter is on

JAN 25,06

Titan is on the 15th.

okay, NOW it's fixed...sorry about that.

[jmknapp]

If anyone has made a animation of the encounter please post it!

It's not the most dynamic animation because the flyby is fairly distant and the range doesn't change very much for a couple days around closest approach. From what I can tell from the public science plans, they're going to make these observations of Iapetus during Jan 24-26:

begin: 2006JAN24 21:04 UTC
end: 2006JAN25 02:03 UTC
range: ~910,000 km
CIRS_020IA_FP3GLOBAL002_PRIME
Global_FP3_map

Long turns (33+34 min.) 2-scan FP3 mosaic of 4 mrad at 4urad/sec (00:34); then FUV, NAC, FP3, FP1 stares (00:49 each). One support image for each stare. Center detectors, 3 cm-1 resolution, shutter closed 00:00-00:05 and 02:45-02:50.

begin: 2006JAN24 21:04 UTC
end: 2006JAN25 02:03 UTC
range: ~910,000 km
CIRS_020IA_FP3GLOBAL002_SI CIRS_020IA_FP3GLOBAL002_SI

Four support images for pointing confirmation. Timing flexible (+/- 10 min or so), with images at approximately NACs at 01:35, 02:20, 03:05, and WAC at 03:55 into observation.

Also the ORS platform will evidently be pointed at Iapetus during the following times, but I can't find a corresponding science plan entry:

Jan 25 11:46 - Jan 25 12:21, range 880,209 - 879,382 km
Jan 26 12:30 - Jan 26 12:51, range 890,464 - 891,246 km

times approximate

Here are the approximate views for these three vantage points:







The Moat is only in Saturnshine for those observations.

They seem to be paying a little closer attention to Iapetus on Jan. 20 with these specific science plan items:

Iapetus limb topography and geodesy observation

ISS_020IA_LIMBTOPOA001_PRIME

begin: 2006JAN20 12:13 UTC
end: 2006JAN20 12:43 UTC

Turn -Y to Iapetus; do 1x1 mosaic 3 NAC clear filters; turn to WP


ICYLON: Longitude / Phase Space Coverage
UVIS_020IA_ICYLON002_ISS

2006JAN20 12:43 UTC
2006JAN20 13:33 UTC

Target to icy satellite. Measure uv albedo across longitude / phase space. Opportunities selected by SOST-ORS consortium. Slit orientation is flexible.


Iapetus global color observation

ISS_020IA_GLOBCOLA001_PRIME

begin: 2006JAN20 12:43 UTC
end: 2006JAN20 13:33 UTC

Do two times 1x1 mosaic 24 NAC color + 9 NAC polarizer + 4 WAC polarizer filters; turn to WP

Here's the view during those observations:



Looks like the Moat will be in sunlight, but the disk pretty small in the NAC view.

[Bjorn Jonsson]

If anyone has made a animation of the encounter please post it!

This and several Iapetus flybys were discussed in a different thread several weeks ago.

This is from that thread and contains a link to an animation I did of the upcoming distant flyby:

http://www.unmannedspaceflight.com/index.p...opic=1627&st=98

[TritonAntares]

Here the planned ISS-observations between january 20th and 28th:
Request ID ______________________ Start UTC ___________ Duration ____ Images
ISS_020IA_LIMBTOPOA001_PRIME ___ 2006-020T12:13:00 ___ 000T00:30 ___ 1 clr, 7 long exp.
ISS_020IA_GLOBCOLA001_PRIME ____ 2006-020T12:43:00 ___ 000T00:50 ___ 4 clr, 25 color, 13 polarizer
ISS_020IA_FP3GLOBAL001_CIRS _____ 2006-022T21:34:00 ___ 000T01:00 ___ 4 clr, 8 color, 9 pol, 8 long exp, a few SI
ISS_020IA_LIMBTOPOD001_PRIME ___ 2006-023T14:01:00 ___ 000T00:15 ___ 2 clr, 4 color, 3 pol, 7 long exp
ISS_020IA_SPECPHOTE001_PRIME ___ 2006-024T12:08:00 ___ 000T00:15 ___ 1 clr, 8 color, 6 pol, 1 long exp
ISS_020IA_GLOBMAPF001_PRIME ____ 2006-025T12:08:00 ___ 000T00:15 ___ 1 clr, 4 color, 6 pol, 2 long exp
ISS_020IA_SPECPHOTG001_PRIME ___ 2006-026T12:38:00 ___ 000T00:15 ___ 1 clr, 4 color, 3 pol, 2 long exp
ISS_020IA_SPECPHOTH001_PRIME ___ 2006-027T04:38:00 ___ 000T00:15 ___ 1 clr, 4 color, 6 pol, 2 long exp
ISS_020IA_SPECPHOTI001_PRIME ___ 2006-028T11:53:00 ___ 000T00:15 ___ 2 clr, 4 color, 6 pol, 1 long exp

17 clr, 61 color, 52 pol, 30 long exp, altogether 160 pics...

Information was given by Tilmann Denk in a German forum.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Is anybody able to create/post an animation for this flyby based on the latest japetus-map:


Also interesting would be an animation similar to this one of the november encounter:


Bye...

[TritonAntares]

Some additional information:

Start UTC ___________ Distance _______ Diameter
2006-020T12:13:00 ___ 1,950 Mio.km ___ 2,5'
2006-020T12:43:00 ___ 1,942 Mio.km ___ 2,5'
2006-022T21:34:00 ___ 1,242 Mio.km ___ 4,0'
2006-023T14:01:00 ___ 1,100 Mio.km ___ 4,5'
2006-024T12:08:00 ___ 0,958 Mio.km ___ 5,2'
2006-025T12:08:00 ___ 0,880 Mio.km ___ 5,6'
2006-026T12:38:00 ___ 0,891 Mio.km ___ 5,5'
2006-027T04:38:00 ___ 0,943 Mio.km ___ 5,2'
2006-028T11:53:00 ___ 1,116 Mio.km ___ 4,4'

[scalbers]

Speaking of Iapetus maps, I'm fine-tuning an updated map with an additional Saturn-shine image. I'm reading this from the JPL raw images page for now, though I hope to use this occasion to learn how to read it from the PDS. The current map version can be seen here:

http://laps.noaa.gov/albers/sos/sos.html#IAPETUS

[Decepticon]

Very Nice!

[Michael Capobian...]

Yes, this map shows the dotted line north of the moat much better than the official one. I'd be interested in seeing an exogenous explanation for it.

Michael

Very Nice!

[JRehling]

Yes, this map shows the dotted line north of the moat much better than the official one. I'd be interested in seeing an exogenous explanation for it.

Michael

I agree. In fact, I'd be interested in seeing a purely endogenous explanation, too!

(I'll interject here, high in my message: continued great work by Steve Albers!)

A purely endogenous explanation (eg, the ridge is a Europa/Enceladus style rift that sprayed the dark stuff out over hundreds of km, painting the surface) is going to have a very hard time explaining the patchy irregularities in eastern CR. One possibility (but a reach) is that the terrain is so extremely rugged that at the furthest reaches of the spray, when the material is coming in almost tangential to the geoid, that pronounced and bizarre topography could allow almost arbitrary complexity in the boundary. Really, any "geyser"ish explanation demands that. And sure enough, we know that Iapetus has, in general, appreciably nonspheroidal topography. But we won't be able to characterize the topography of eastern CR within the primary mission -- that would have to remain an ad hoc explanation. Even that seems to strain credulity at the Snowman craters, where the topography can only be so irregular (is a crater still vaguely bowl-shaped or not)? We can similarly (almost!) reject the exogenous explanations that have Iapetus having passed (in one event or many) through a cloud of material. The bizarre boundary of eastern CR is implausible in that case.

An endogenous explanation holding that the dark stuff flooded upwards can already be rejected. The northern boundary clearly shows that the dark stuff was emplaced by ballistic delivery from the south.

I think we're going to be left to conclude that the material sprayed outward from the surface of Iapetus, within what is now CR, in a fashion much more energetic and irregular than geysers could plausibly explain, and that some sort of impact event led to the staining of Iapetus.

The remaining flybys are going to show us western CR at very high resolution, and the southern boundary at decent resolution. We will not see the eastern/Snowman region in very high resolution (and sunlight rather than saturnshine) at all during the primary mission -- excepting decent coverage as Cassini departs the Sept. 2007 flyby and eventually the Snowman will rotate in.

For the sake of discussing whether or not Iaptus merits more flybys in the extended mission, I think not. The remaining flybys are going to show so much of the hardly-seen boundaries of CR at higher resolution that I can't see dedicating another flyby to finish the almost-complete map. ALTHOUGH, the one portion of the border that will not be mapped may be the single most intriguing! The big Snowman crater will be seen at about 1.3 million km distance in Sept 2007. A flyby to see that same region at higher resolution seems like a big cost for a small gain. In the absence of other reasons to have apoapsis be so far out, I would expect the extended mission to pull the apoapsis way in, so Titan encounters happen much more frequently, and the RADAR mapping can add a swath or two per month instead of a swath every few months.

[Guest_BruceMoomaw_*]

Well, during the planning for the primary mission Iapetus was officially listed as the third most interesting moon, right after Enceladus (Dione, for some reason, was fourth). I have trouble seeing them omitting at least a second Iapetus flyby, although I doubt we'll see a third one.

[alan]

Yes, this map shows the dotted line north of the moat much better than the official one. I'd be interested in seeing an exogenous explanation for it.

Michael

This abstract may explain some of the dark features on the trailing side

....The Phoebe-dust model is very compelling because it naturally explains why the leading face of Iapetus, the side that is receiving dust from Phoebe, is dark. The model has not gained universal acceptance, however, primarily due to the following dynamical problems: i) the distribution of dark material on Iapetus does not precisely match predicted contours of constant dust flux from Phoebe, ii) there are dark-floored craters in Iapetus' high-albedo hemisphere...These problems are greatly reduced with the realization that Iapetus took nearly a billion years to become tidally locked to Saturn. I suggest the following scenario for the origin of the black/while dichotomy on Iapetus. Phoebe was probably captured early in the Solar System's history, well before Iapetus' spin slowed to its present synchronous rate. While Iapetus was spinning rapidly, dust from Phoebe accumulated at all longitudes on Iapetus uniformly..... After Iapetus became tidally locked, its trailing side was shielded from Phoebe dust, and volatile ice accumulated there burying the dark Phoebe material. Large impacts on the trailing side have dredged up some ancient Phoebe debris, creating the dark-floored craters..... Since the distribution of Iapetus' dark material depends on the flux of Phoebe dust over 4.5 billion years, it is not surprising that the distribution does not precisely match predictions which consider only the present dynamical configurations of the two satellites.

http://adsabs.harvard.edu/cgi-bin/nph-bib_...43b1f26c2909851

The mote around the snowman crater and the linear features may be dark material uncovered by landslides along the crater rim and Dione like fractures